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Number of 6-element families of an n-element set such that every 3 members of the family have a nonempty intersection.
1

%I #13 Oct 08 2017 13:26:09

%S 0,0,0,0,112,40286,5485032,534844548,45066853496,3538771308282,

%T 267882021563464,19861835713621616,1453175611052688600,

%U 105278656040052332838,7564280930105061931496,539399446172552069053404

%N Number of 6-element families of an n-element set such that every 3 members of the family have a nonempty intersection.

%D V. Jovovic, G. Kilibarda, On the number of Boolean functions in the Post classes F^{mu}_8, Diskretnaya Matematika, 11 (1999), no. 4, 127-138 (translated in Discrete Mathematics and Applications, 9, (1999), no. 6).

%H G. C. Greubel, <a href="/A051363/b051363.txt">Table of n, a(n) for n = 0..550</a>

%F a(n) = (1/6!)*(64^n -20*56^n +90*52^n +30*50^n +25*49^n -420*48^n -180*47^n +450*46^n +60*45^n +615*44^n +1683*43^n -3252*42^n -6030*41^n +8520*40^n +10560*39^n -15849*38^n -13005*37^n +26410*36^n +10655*35^n -50385*34^n +33390*33^n +29480*32^n -82010*31^n +91215*30^n -67380*29^n +36870*28^n -15249*27^n +4380*26^n -1215*25^n +1390*24^n -695*23^n -1574*22^n +3255*21^n -3075*20^n +1800*19^n -675*18^n +150*17^n +70*16^n -340*14^n +510*13^n -340*12^n +85*11^n -225*8^n +225*7^n +274*4^n -274*3^n -120*2^n +120).

%Y Cf. A036239, A051180, A051181, A051182, A051183, A051184, A051185.

%K nonn

%O 0,5

%A _Vladeta Jovovic_, Goran Kilibarda